Mars and the Stellar Imposter

Have you been watching Mars in our evening skies? Mars and Saturn are visible in the southwest as soon as the Sun sets, looking like bright stars. Saturn sets pretty quickly after sunset, but Mars doesn't set until 8:30 PM. See the image below set for Peoria just after sunset, around 7 PM.

See Mars and Saturn just after sunset in the southwest. Image Credit: Stellarium.

If you are observing Mars, you might notice that it is close to a star that looks quite a bit like the red planet in our sky. The star is red, and just about the same brightness. It is called Antares, which derives from the ancient Greek word Άντάρης, which means "equal to Ares". Ares is the Greek god of war, equivalent to the Roman god of war, Mars, for whom the planet is named. Clearly the ancients noticed that the wandering planet Mars and the star Antares look a great deal alike! See the image below, set for Peoria at about 7:45 PM.

Mars and Antares, close in proximity and appearance in our evening sky. Image credit: Stellarium.

Antares is the brightest star in Scorpius the Scorpion, and is often referred to as the heart of the Scorpion. You can read more about Scorpius here. Antares is a red supergiant star; you could line up almost 900 Suns across its diameter and squeeze hundreds of millions of our star inside of it! 

Antares is huge! Notice the (giant) star Arcturus as a comparison. I wrote about Arcturus and Bootes here. Image credit: Wikipedia Commons.

Because it is a supergiant, we know it has already exhausted the hydrogen in its core, and is in the process of "burning" heavier elements. When it converts enough of its core into iron, the core will collapse and the star will explode in a supernova. The gas blown off from the collapsed star will form a supernova remnant, an enormous bubble of gas expanding at millions of miles per hour.

Kepler's Supernova remnant, SN 1604, was observed in 1604 - the last supernova to be observed in our galaxy. The beautiful (false) colors in this image represent wavelengths of light, invisible to our eyes, eg. xrays. Image Credit: NASA

Antares could explode sometime in the next million years or so. But because it is about 550 light years away, we won't be able to tell it went supernova until 550 years later. In fact, it could have already exploded and we just don't know it yet!

And speaking of Mars, there are two new spacecraft orbiting the red planet! The India Space Research Organization sent its first interplanetary mission to Mars, the Mars Orbiter Mission. 

Image Credit: ISRO.

And NASA's MAVEN mission just entered orbit around Mars as well! MAVEN will be studying Mars' atmosphere, helping scientists understand how Mars lost its atmosphere over time. 

So next time you are out after sunset, find Mars and Antares in the sky. Imagine how big Antares is, and how long it takes the light from this massive star to get to us. Marvel at our ability to explore Mars - there are 7 missions at Mars right now! 

And if you are thirsty for the latest news from space, join us at the Dome Planetarium for Wine and Cheese Under the Stars on October 24, from 7-9 PM. We will enjoy wine from Kickapoo Creek Winery and geek out together!